(a) Field of the Invention
The present invention relates to a precoding method and apparatus.
(b) Description of the Related Art
When a plurality of transmission/reception nodes perform communication using the same resource, each transmission node precodes a transmission signal in order to reduce an influence of an interference signal or increase strength thereof, relative to an interference signal. Here, precoding refers to applying a precoder to a transmission signal, and a precoder may be called a precoding matrix, a precoding vector, a beamforming matrix, or a beamforming vector.
In a Gaussian interference channel including a plurality of transmission/reception nodes, it is known that, when each node causes interference or is interfered with, if a ratio of an interference signal strength to noise strength is smaller than a certain value, interference is assumed to be noise in processing signals to achieve the sum of the overall capacity.
In a case that strength of an interference signal is too strong to be disregarded, an algorithm for iteratively calculating a transmission filter and a reception filter and determining a transmission filter having a predetermined amount of calculation lower than a predetermined reference value, as a precoder, has been known.
Such an algorithm iteratively calculates a transmission filter and a reception filter in the process of calculating a precoder, and here, since the number of repetitions is great, an amount of calculation is increased, and since feedback channel information is instantaneous information, an amount of feedback is increased.